A Critical Role of the Transcription Factor Fli‐1 in Murine Lupus Development by Regulation of Interleukin‐6 Expression

Abstract

Objective The Fli-1 transcription factor is implicated in the pathogenesis of systemic lupus erythematosus (SLE) in both human patients and animal models. Dysregulation of interleukin 6 (IL-6) is also associated with SLE. We investigated whether Fli-1 directly regulates the expression of IL-6. Methods Sera were collected from wild-type and Fli-1 heterozygous (Fli-1+/−) MRL/lpr mice and the concentration of IL-6 was measured by ELISA. Expression of IL-6 in the kidney was measured by real-time PCR. T cells were isolated from wild-type and Fli-1+/− MRL/lpr mice and stimulated with CD3/CD28 beads, and the concentration of IL-6 in the supernatants was measured by ELISA. MS1 endothelial cells were transfected with Fli-1 and control siRNA, and the production of IL-6 was compared after lipopolysaccharides (LPS) stimulation. A chromatin immunoprecipitation (ChIP) assay was performed to determine whether Fli-1binds to the IL-6 promoter region. Transient transfections with the NIH 3T3 cell line were performed to study if Fli-1 regulates the expression of IL-6. Results Fli-1+/− MRL/lpr mice had significantly decreased IL-6 in sera and reduced expression of IL-6 in kidneys compared to wild-type littermates. The T cells isolated from Fli-1+/− MRL/lpr mice produced less IL-6. Inhibiting the expression of Fli-1 in endothelial cells resulted in reduced production of IL-6. The ChIP assay revealed direct binding of Fli-1 to three regions within the IL-6 promoter. Fli-1 activated transcription from the IL-6 promoter in a dose-dependent manner. Conclusion Fli-1 directly regulates IL-6 expression as one of possible mechanisms for the protective effect in lupus of decreased Fli-1 expression.

Epigenomic Profiling of Human CD4+ T Cells Supports a Linear Differentiation Model and Highlights Molecular Regulators of Memory Development

“…Other prime TF candidates include TFs previously implicated in Tmem regulation such as RUNX3, E2F2, LEF1, BCL6, or members of the ELF-, KLF-, or FOXJ-families, as well as CREB1, ETS-1, and JUN-FOS, which are known to be involved in multiple cellular processes of differentiation and activation. Additional interesting candidates include (1) the aryl hydrocarbon receptor, AHR, which has been implicated in differentiation of CD4 + T cells into pro-or anti-inflammatory subsets and, hence, to modulate autoimmune diseases in various animal models (reviewed in Esser et al, 2009;Hanieh, 2014) and (2) the ets-family member FLI-1, which has been reported to affect thymic T cell development, TCR signaling, glycosphingolipid metabolism, and cytokine expression and has been implicated in autoimmune diseases, too (Richard et al, 2013;Sato et al, 2014). Others of the top-predicted TFs have not been directly associated to regulation of Tmem differentiation yet, but are players in potentially relevant cellular processes, such as intracellular signaling (RFX3, via the RAS-MAPK pathway), metabolic processes (NRF1 and SREBF1, associated with mTORC1 signaling), and chromatin remodeling (ZFP161, targeting of the repressive Polycomp complex).…”

FLI1 Levels Impact CXCR3 Expression and Renal Infiltration of T Cells and Renal Glycosphingolipid Metabolism in the MRL/lpr Lupus Mouse Strain

“…MRL/lpr Fli1 +/+ immune cells, including T cells, do not readily migrate to the kidney when transferred into MRL/lpr Fli1 +/− mice (10). Chemokines Ccl2 ( Mcp-1 ), Ccl3 ( Mip-1α ), Ccl4 ( Mip-1β ) and Ccl5 ( Rantes ) are significantly decreased at the message level in the kidneys of MRL/lpr Fli1 +/− compared to Fli1 +/+ mice and FLI1 was demonstrated to regulate the promoter activity of several different cytokine genes in endothelial cells (8, 9, 12, 13). Here we demonstrated that the expression Cxcl9 and Cxcl10 , CXCR3 ligands, also are significantly decreased in the kidneys of MRL/lpr Fli1 +/− compared to the Fli1 +/+ mice.…”

“…6E sequence) and/or non-canonical ETS binding site that remains to be identified. The putative ETS sites in hCXCR3 tested for FLI1 binding were chosen based on numerous studies, including some from our laboratory, demonstrating that FLI1 binds and acts through conserved canonical ETS sites that are more proximal to the transcription start site (9, 12, 17, 34–41). However, we recently demonstrated that FLI1 also can regulate promoters through more distal sites (12, 13).…”

“…NZM2410 mice with reduced FLI1 levels ( Fli1 +/− ) were shown to have decreased numbers of renal infiltrating inflammatory cells (11). Recent studies demonstrated that FLI1 regulates the expression of MCP-1, RANTES and IL-6 (9, 12, 13). Together, these studies suggest that globally reducing FLI1 levels in lupus mouse strains improves disease by decreasing renal chemokine production and thus, inflammatory infiltration.…”

Loss of PAFR prevents neuroinflammation and brain dysfunction after traumatic brain injury

“…The sequences of the forward and reverse primers are listed in Table 1. The RT-PCR program has been previously desribed54. The threshold cycle (Ct) was calculated using the second-derivative maximum method and data were calculated via the delta−delta method.…”